JP5450576B2 - Touch switch device - Google Patents

Description

  The present invention relates to a touch switch device that detects a touch operation with a finger of a user.

  2. Description of the Related Art Conventionally, a detection device that includes a single touch detection unit that detects an operation state of a touch switch for a plurality of touch switches, and sequentially switches connections between the touch switches and the touch detection unit using a switching element. It has been proposed (see, for example, Patent Document 1). According to the detection device described in Patent Literature 1, it is possible to reduce the cost of the detection device as compared to the case where a touch detection unit is individually provided for each touch switch.

  Further, a capacitance type detection device using a capacitance sensor that detects a person or an object existing between electrodes based on a change in capacitance between a pair of electrodes arranged opposite to each other has been proposed ( For example, see Patent Document 2). In the capacitance type detection device described in Patent Document 2, an auxiliary electrode provided to face one of a pair of electrodes is operated, and the same state as when a person or an object exists between the pair of electrodes Capacitance sensors are self-diagnosed by forcibly creating them.

JP 2009-71708 A (page 24, FIG. 26) Japanese Patent Laid-Open No. 2001-264007 (page 6-7, FIG. 10)

  When detecting operation states of a plurality of touch switches as in the detection device described in Patent Document 1, as described in Patent Document 2, an auxiliary electrode is provided for each touch switch to perform self-diagnosis. Thus, the reliability of the detection device can be improved.

  However, when an auxiliary electrode is provided for each touch switch, the structure of the touch switch becomes complicated, and the operation status of the touch switch cannot be detected during the self-diagnosis of each touch switch. There is.

  Therefore, for example, in a touch switch device that is provided in a gas stove and detects the operation state of a plurality of touch switches that instruct the gas stove to be ignited and extinguished, the self-diagnosis function of each touch switch is not provided. There is also adopted a configuration including a plurality of touch switches for extinguishing the gas stove. With this configuration, even if one touch switch breaks down during combustion of the gas stove, the gas stove can be extinguished by another touch switch.

  In this way, the failure of the touch switch itself can be dealt with by providing redundancy such as assigning a plurality of touch switches. However, when the touch detection unit breaks down, it becomes impossible to detect the operation state of all the touch switches, and in the example of the gas stove, the gas stove cannot be extinguished.

  The present invention has been made in view of such a background, and an object thereof is to provide a touch switch device that can detect a failure of a touch detection unit that detects an operation state of a plurality of touch switches.

The present invention has been made to achieve the above object, and the touch switch device of the present invention includes:
A detection terminal portion having a plurality of first detection terminals and one second detection terminal;
A plurality of touch switches having touch electrodes, the touch electrodes individually connected to any of the plurality of first detection terminals;
Pseudo touch operation having two capacitors connected in series between a ground potential portion and the second detection terminal, and a switching element connected between a connection portion between the two capacitors and the ground potential portion Circuit,
A touch detection unit having a detection input terminal and detecting a capacitance between the detection input terminal and the ground potential unit;
A selection circuit that selects any one of the plurality of first detection terminals and the second detection terminals of the detection terminal unit and connects to the detection input terminal of the touch detection unit;
In a state where the second detection terminal of the detection terminal unit is connected to the detection input terminal of the touch detection unit by the selection circuit, the first electrostatic capacitance detected by the touch detection unit when the switching element is turned on. A failure detection unit that detects a failure of the touch detection unit based on a difference between a capacitance and a second capacitance detected by the touch detection unit when the switching element is in a cut-off state; (First invention).

  According to the first invention, the failure detection unit connects the second detection terminal of the detection terminal unit and the detection input terminal of the touch detection unit by the selection circuit, and the switching element of the pseudo touch operation circuit Is switched between a conduction state and a cutoff state, and the first capacitance and the second capacitance are detected.

  Here, if the touch detection unit is operating normally, when the switch element is switched between a conduction state and a cutoff state, a change in capacitance between the second detection terminal and the ground potential unit causes the first There is a difference between one capacitance and the second capacitance. On the other hand, when the touch detection unit is out of order, such a difference between the first capacitance and the second capacitance does not occur. Therefore, the failure detection unit can detect a failure of the touch detection unit based on the difference between the first capacitance and the second capacitance.

  In the first aspect of the invention, the capacitance of the two capacitors is such that when the touch detection unit is operating normally, the first capacitance is the touch electrode of any of the plurality of touch switches. When the touch switch is connected to the detection input terminal of the touch detection unit and the touch switch is operated, the first detection value is an assumed value of the capacitance detected by the touch detection unit, When the second capacitance is in a non-touch state in which any one of the touch electrodes of the plurality of touch switches is connected to the detection input terminal of the touch detection unit and the touch switch is not operated. The second detection value is set to be a second assumed value that is an assumed value of the capacitance detected by the touch detection unit (second invention).

  According to a second aspect of the present invention, the capacitance of the two capacitors is set according to the capacitance detected by the touch detection unit when the touch switch is in a touched state and in a non-touched state. It is possible to detect a failure of the detection unit with higher accuracy.

  In the first or second aspect of the invention, the switching element is provided in a microcomputer and is connected between an output terminal of the microcomputer connected to a connection portion between the two capacitors and a ground potential portion. It is connected (3rd invention).

  According to the third invention, the switching element provided in the microcomputer is connected between the output terminal of the microcomputer and a connection portion between the two capacitors. In this case, generally, the parasitic capacitance of the output portion of the switching element used for the output terminal of the microcomputer is smaller than the parasitic capacitance of the output portion of the switching element such as a general-purpose FET.

  Therefore, when the second capacitance is detected by the touch detection unit, the proportion of the parasitic capacitance of the output unit of the switching element in the cut-off state is reduced in the second capacitance, The detection accuracy of the second capacitance can be increased.

The block diagram of a touch switch apparatus. The transition diagram of the detection state by a touch detection part. The block diagram in another embodiment of a touch switch apparatus.

  An embodiment of the present invention will be described with reference to FIGS. With reference to FIG. 1, the touch switch device 1 of the present embodiment includes a plurality of touch switches 62 in which touch electrodes 73, 75, 77 are attached in close contact with the back surface of a dielectric panel (glass plate or the like) not shown. To 64 operation states (with / without touch) are detected.

  The touch switch device 1 includes a microcomputer 10 connected to the touch switches 62 to 64, an adjustment circuit 80, and a pseudo touch operation circuit 61. The microcomputer 10 has a function of detecting whether or not a plurality of touch switches are operated. In the present embodiment, the touch operations similar to the three touch switches 62 to 64 and the touch switches 62 to 64 are performed. The operation state of the pseudo touch operation circuit 61 that artificially creates the situation is detected.

  The microcomputer 10 executes a control program for the touch switch device 1 held in a memory (not shown), thereby operating the touch switches 62 to 64 and the pseudo touch operation circuit 61 (with / without touch). ) And a failure detection unit 12 that detects a failure of the touch detection unit 11.

  The touch electrodes 73, 75, and 77 of the plurality of touch switches 62 to 64 are individually connected to the detection terminals 42 to 44 (corresponding to the first detection terminal of the present invention) of the detection terminal unit 40 of the microcomputer 10. ing. In the figure, reference numerals 74, 76, and 78 denote capacitances that change in response to a touch operation by a user's finger.

  The pseudo touch operation circuit 61 includes two capacitors 71 and 72 connected in series between the detection terminal 41 (corresponding to the second detection terminal of the present invention) of the detection terminal unit 40 and the ground potential unit. The switching element 70 (FET, transistor, etc.) connected between the connection location between the capacitors 71 and 72 and the ground potential portion is provided.

  The control input terminal of the switching element 70 is connected to the output port 21 of the microcomputer 10, and the internal switching element 20 (FET, transistor, etc.) is connected between the output port 21 and the ground potential portion in the microcomputer 10. . The internal switching element 20 switches between a conduction state (a state where the output port 21 is conducted to the ground potential portion) and a cutoff state (a state where the output port 21 is in a high impedance state) according to a control signal from the failure detection unit 12. .

  When the output port 21 is in a high impedance state, the switching element 70 is in a conductive state. Further, when the output port 21 is in a state of being conducted to the ground potential portion, the switching element 70 is cut off.

  The selection circuit 13 individually connects the detection terminals 41 to 44 of the detection terminal unit 40 to the detection input terminals 51 to 54 of the touch detection unit 11 via selection switches 31 to 34. The selection circuit 13 selects any one of the detection terminals 41 to 44 by bringing only one of the selection switches 31 to 34 into a conductive state, and detects input of the touch detection unit 11. Connect to terminals 51-54.

  The adjustment circuit 80 includes a capacitor 81, a resistor 82, and a capacitor 83 connected in series between the CHa terminal of the touch detection unit 11 and the ground potential unit. The connection point between the capacitor 81 and the resistor 82 is connected to the CHb terminal of the touch detection unit 11, and the connection point between the resistor 82 and the capacitor 83 is connected to the CHc terminal of the touch detection unit 11.

  The touch detection unit 11 uses the selection circuit 13 to sequentially connect any one of the touch switches 62 to 64 and the pseudo touch operation circuit 61 to any one of the corresponding detection input terminals 51 to 54, thereby changing the capacitance. By detecting, the operation state of the connected touch switches 62 to 64 and the operation state (pseudo operation state) of the pseudo touch operation circuit 61 are detected.

The touch detection unit 11 operates the detection state (touch switches 62 to 64 or the pseudo touch operation circuit 61) connected to any of the detection input terminals 51 to 54 according to the following procedures (1) to (6). Detects touch / no touch.
(1) The capacitor 83 is charged by setting the CHc terminal to the power supply voltage level.
(2) After the charging of the capacitor 83 is completed, the CHc terminal is set to high impedance, the CHb terminal is set to the ground potential for a short time, and the capacitor 83 is discharged through the resistor 82.
(3) After discharging for a short time, the CHb terminal is set to high impedance, and the voltage Va at the CHa terminal is measured. Va is represented by the following formula (1).

However, Va: voltage of the CHa terminal, Cr: capacitance of the capacitor 81, Cx: detection target connected to the touch detection unit 11 via the selection circuit 13 (of the touch switches 62 to 64 and the pseudo touch operation circuit 61) The capacitance of Vc: CHc terminal.
(4) Thereafter, the discharge and Va measurement in (2) and (3) above are repeated, and the number of discharges until Va falls below the threshold voltage Vth is counted.
(5) The processes (1) to (4) are performed a predetermined number of times (for example, four times), and the count value (discharge count value) of the predetermined number of discharges is averaged to determine the capacitance of the detection target. Measured value.
(6) When the measured value is a preset touch detection range, it is determined as “touch present”, and when the measured value is a preset non-touch detection range, it is determined as “no touch”.

  In the touch switches 62 to 64, when the user's finger approaches the touch electrodes 73, 75, 77, the capacitance Cx increases, and Va decreases from the above equation (1). Therefore, the discharge count value until Va falls below the threshold voltage Vth decreases, and the measurement value output from the touch detection unit 11 decreases.

  Next, the failure detection process of the touch detection unit 11 by the failure detection unit 12 will be described. The failure detection unit 12 sets only the selection switch 31 of the selection circuit 13 to the conductive state, sets the other selection switches 32 to 34 to the cutoff state, and sets the detection target by the touch detection unit 11 as the pseudo touch operation circuit 61.

  And the failure detection part 12 makes the switching element 70 a conduction | electrical_connection state, and acquires the measurement output (equivalent to the 1st electrostatic capacitance of this invention) by the touch detection part 11. FIG. Further, the failure detection unit 12 acquires the measurement output (corresponding to the second capacitance of the present invention) by the touch detection unit 11 with the switching element 70 in the cut-off state.

  Here, the capacitance Cs1 of the pseudo touch operation circuit 61 when the switching element 70 is in a conductive state is expressed by the following equation (2).

  However, Cs1: Capacitance of the pseudo touch operation circuit 61 when the switching element 70 is turned on, C1: Capacitance of the capacitor 71 of the pseudo touch operation circuit 61

  Further, the capacitance Cs2 of the pseudo touch operation circuit 61 when the switching element 70 is in the cutoff state is expressed by the following equation (3).

  However, Cs2: Capacitance of the pseudo touch operation circuit 61 when the switching element 70 is shut off, C1: Capacitance of the capacitor 71 of the pseudo touch operation circuit 61, C2: Capacitance of the capacitor 72 of the pseudo touch operation circuit 61 Capacitance.

  Here, regarding the electrostatic capacitance C1 of the capacitor 71 and the electrostatic capacitance C2 of the capacitor 72, Cs1 is a predetermined value within the touch detection range (corresponding to the first assumed value of the present invention), and Cs2 is the above non-existing value. It is set to be a predetermined value (corresponding to the second assumed value of the present invention) within the touch detection range.

  Then, when the switching element 70 is switched between the conduction state and the cutoff state when the touch detection unit 11 is operating normally, as shown in FIG. 2, when the switching element 70 is in the conduction state (from t1 to t1). t2, t3 to t4, t5 to t6, t7 to t8) are detected by the touch detection unit 11 as “touch present”. Further, when the switching element 70 is in the cut-off state (t2 to t3, t4 to t5, t6 to t7), the touch detection unit 11 detects “no touch”.

  On the other hand, when the touch detection unit 11 is out of order, the detection result of the operation state based on the measurement output of the touch detection unit 11 is, for example, “no touch” regardless of the capacitance of the detection target (OFF failure). ), A situation different from that during normal operation, such as “with touch” (ON failure) regardless of the capacitance of the detection target.

  Therefore, when the detection result of the operation state based on the measurement output of the touch detection unit 11 is different from that during normal operation, the failure detection unit 12 determines that the touch detection unit 11 has failed. Then, failure notification is performed by turning on an error lamp (not shown).

  Next, FIG. 3 is a configuration diagram of another embodiment of the touch switch device. The touch switch device 1a shown in FIG. 3 is different from the touch switch device 1 shown in FIG. 1 only in the configuration of the pseudo touch operation circuit 61a, and the other configurations are the same.

  In the pseudo touch operation circuit 61 of the touch switch device 1 shown in FIG. 1, a switching element 70 such as an FET is operated by a signal from the output port 21 of the microcomputer 10 to ground the connection portion between the capacitors 71 and 72. Conduction was made to the potential part. In this configuration, the above equation (3) is expressed by the parasitic capacitance 90 (see FIG. 1) between the output terminals when the switching element 70 is in the cutoff state (between the drain and source when the switching element is an FET). Actually, the following equation (4) is obtained.

  However, Cs2 ′: the capacitance of the pseudo touch operation circuit 61 when the switching element 70 is turned off in consideration of the parasitic capacitance, C1: the capacitance of the capacitor 71 of the pseudo touch operation circuit 61, C2: the pseudo touch Capacitance of capacitor 72 of operation circuit 61, Cp: parasitic capacitance between output terminals of switching element 70.

  Comparing equation (3) and equation (4), Cs2 'according to equation (4) is smaller than CS2 according to equation (3). For example, when C1 = 15 (pF), C2 = 30 (pF), and Cp = 10 (pF), Cs2 = 10 (pF) and Cs2 ′ = 11 (pF). Then, Cs1 according to the above equation (2) is Cs1 = 15 (pF) regardless of the parasitic capacitance.

  Therefore, due to the influence of the parasitic capacitance, the difference in capacitance between when the switching element 70 is in the conductive state and when it is in the cutoff state is Cs1−Cs2 = 15−10 = 5 (pF), and Cs1−Cs2 ′. = 15-11 = 4 (pF).

  Therefore, in the pseudo touch operation circuit 61 a of FIG. 3, the output port 21 of the microcomputer 10 is directly connected to a connection portion between the capacitors 71 and 72. In this configuration, the internal switching element 20 corresponds to the switching element of the present invention.

  The parasitic capacitance of the output portion of the internal switching element 20 of the microcomputer 10 is, for example, about 3.0 pF, and can be expected to be smaller than the parasitic capacitance (for example, about 8.0 pF) of the output portion of the FET. Therefore, when Cp in the above equation (4) is decreased and the pseudo touch operation circuit 61a is set in the pseudo touch operation state (the state in which the output port 21 is connected to the ground potential portion), the pseudo non-touch operation state ( It is possible to increase the difference in capacitance of the pseudo touch operation circuit 61a from when the output port 21 is in a high impedance state. Thereby, the failure detection unit 12 can detect the failure of the touch detection unit 11 with higher accuracy.

  In the present embodiment, the touch switch devices 1 and 1a including the four detection terminals 41 to 44 that can be connected to the touch switch are shown. However, the touch switch devices 1 and 1a include two or more detection terminals and are connected to the detection terminals. The present invention can be applied to any touch switch device that detects an operation state of a touch switch using a common touch detection unit.

  In addition, when the touch switch device of the present invention is provided in a heating device such as a gas stove and instructions for starting and stopping the heating means (burner, heater, etc.) are given by the touch switch, A failure of the touch detection unit may be periodically performed, and when the failure of the touch detection unit is detected, the operation of the heating unit may be forcibly stopped.

  In the present embodiment, the capacitances of the capacitors 71 and 72 of the pseudo touch operation circuit 61 are connected to the touch detection unit 11 by the selection circuit 13 so that the switching element 70 is turned on. Sometimes the capacitance (first capacitance) detected by the touch detection unit 11 falls within the touch detection range, and the capacitance detected by the touch detection unit 11 when the switching element 70 is in a cut-off state. (Second capacitance) is set to be within the non-touch detection range, but is not limited to this setting, so that the first capacitance and the second capacitance are somewhat different. What is necessary is just to set the electrostatic capacitance of the capacitors 71 and 72.

  DESCRIPTION OF SYMBOLS 1, 1a ... Touch switch apparatus, 10 ... Microcomputer, 11 ... Touch detection part, 12 ... Failure detection part, 13 ... Selection circuit, 40 ... Detection terminal part, 41-44 ... Detection terminal, 61 ... Pseudo touch operation circuit, 62-64 ... touch switch, 70 ... switching element, 71, 72 ... (capacitor connected in series), 73, 75, 77 ... touch electrode, 80 ... adjustment circuit.

Claims (3)

A detection terminal portion having a plurality of first detection terminals and one second detection terminal;
A plurality of touch switches having touch electrodes, the touch electrodes individually connected to any of the plurality of first detection terminals;
Pseudo touch operation having two capacitors connected in series between a ground potential portion and the second detection terminal, and a switching element connected between a connection portion between the two capacitors and the ground potential portion Circuit,
A touch detection unit having a detection input terminal and detecting a capacitance between the detection input terminal and the ground potential unit;
A selection circuit that selects any one of the plurality of first detection terminals and the second detection terminals of the detection terminal unit and connects to the detection input terminal of the touch detection unit;
In a state where the second detection terminal of the detection terminal unit is connected to the detection input terminal of the touch detection unit by the selection circuit, the first electrostatic capacitance detected by the touch detection unit when the switching element is turned on. A failure detection unit that detects a failure of the touch detection unit based on a difference between a capacitance and a second capacitance detected by the touch detection unit when the switching element is in a cut-off state; A touch switch device. The touch switch device according to claim 1,
The capacitance of the two capacitors is such that when the touch detection unit is operating normally, the first capacitance is detected by the touch electrode of any of the plurality of touch switches. A first assumed value that is an assumed value of the capacitance detected by the touch detection unit when the touch switch is connected and connected to a terminal and the touch switch is operated; The capacitance is detected by the touch detection unit when any touch electrode of the plurality of touch switches is connected to the detection input terminal of the touch detection unit and the touch switch is not operated. The touch switch device is set to have a second assumed value that is an assumed value of the capacitance to be performed. In the touch switch device according to claim 1 or 2,
The touch switch is provided in a microcomputer, and is connected between an output terminal of the microcomputer connected to a connection portion between the two capacitors and a ground potential portion. apparatus.

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